Intestinal conjugation plays an important role in the metabolism of xenobiotics. Enzymes in this tissue may conjugate xenobiotics as they are absorbed from the diet, if they are in a form which can be conjugated, or if they are metabolized in the stomach or intestinal tract to substances which can be conjugated. Also, they may reconjugate substances which are hydrolyzed while undergoing enterohepatic recirculation. Little is known of intestinal xenobiotic conjugating enzymes. They are usually latent such that maximum activity is only observed by solubilization with detergent. However, high concentration of detergents inactivate the enzymes. We have undertaken a study of a rabbit intestinal enzyme for the conjugation of p-nitrophenol with glucuronic acid. The ultimate objective will be to study the role and significance of the enzyme in the metabolism of xenobiotics. The enzyme can be solubilized with octyl glucoside and partially purified by column chromotography of DEAE Sephacel and octylamine-Sepharose 4B. Most of the properties of the enzyme can probably be distributed to associate lipids, which currently are being studied.